Feedback inhibition refers to a form of metabolic regulation in which the end products of a metabolic pathway inhibit an enzyme that catalyzes one of the steps in the pathway, thus turning down the rate at which that pathway produces
product.
(Figure 6.16)

Catalyst

chemical substance that accelerates the rate at which a reaction occurs without itself being consumed during the reaction. Catalysts act by lowering the activation energy.

activation energy

energy barrier that must be overcome before reactions can proceed (the energy that must be put in to get the reaction to go)

enzyme

biological catalyst, typically a protein (although there are examples of RNA enzymes, called ribozymes)

substrate

reactant molecule recognized (bound by) an enzyme

active site

region (site) within the enzyme molecule where the substrate binds and where catalysis occurs

allosteric site

region (site) separate and distinct from the active site where allosteric effector (or
egulator) molecules bind to the enzyme

inhibitor

molecule that binds to the enzyme and in so doing, reduces its catalytic activity
(decreases the rate of the reaction)

metabolism

all the chemical reactions that take place within a living organism

catabolic pathways

degradative processes in which complex molecules are broken down into simpler molecules to release energy
(example: polymers are broken down to monomers
via hydrolysis reactions)

potential energy

energy with the potential to be released

kinetic energy

the energy of motion, which is directly related to the speed of that motion. Moving matter does work by transferring some of its kinetic energy to other
matter that it interacts with.

energy

the capacity to do work

energy

the capacity to do work

1st and 2nd laws of thermodynamics

the laws that govern energy transformations in organisms and other collections of
matter.

1st law of thermodynamics states that "energy can be transformed and
transferred, but it can be neither created nor destroyed".

2nd law of
thermodynamics states that "every energy transfer or transformation increases the
entropy of the universe", usually in the form of heat.

free energy

the portion of a system's energy that is available to do work

equilibrium

with respect to a chemical reaction, the point when there is no further change in
the concentration of products and reactants;

also refers to the point in a reaction when the free energy is lowest (as move towards equilibrium, free energy decreases; as move away from equilibrium, the free energy increases).

cooperativity

a mechanism for increasing enzyme activity that is observed only in enzymes
comprised of 2 or more subunits, each of which has an active site: binding of one
substrate molecule alters the conformation of the enzyme so that it more readily
binds additional substrate molecule
(FIGURE 6.15)

The binding of substrate to the active site of the enzyme induces a slight change in
the conformation (shape) of the enzyme such that there is a better fit between the
substrate and the enzyme

Distiniguish between a competitive and non-competitive inhibitor. (in regard to rate of reaction, Km, Vmax)

Competitive:
binds to the active site, Km increases; at low [substrate], inhibitor ↓
reaction rate; however, this inhibition can be overcome at high [substrate], Vmax is
the same

Noncompetitive:
binds to enzyme at site other than the active site inducing a
change in the conformation of the enzyme molecule. In most cases Km remains the same. The rate is decreased at low [substrate]. There is a lower Vmax;
inhibition cannot be overcome by high [substrate],

Feedback inhibition refers to a form of metabolic regulation in which the endproducts of a metabolic pathway inhibit an enzyme that catalyzes one of the steps in the pathway, thus turning down the rate at which that pathway produces
product. (see figure 6.16 in your text for an example). Allosteric regulation is
important because it prevents the cell from wasting resources (prevents cell from
making products it has sufficient quantities of); also prevents the potentially toxic
buildup of products in the cell.

The 1st law tells us that energy can be incoverted but not destroyed, while the 2nd law says there is always a price to pay in conversion.

What is the that price and how does it relate to biological processes?

The price to pay is energy lost in every chemical reaction in the form of heat (entropy). This is relevant to biological systems because it means that chemical
reactions in cells are not 100% efficient, and that energy must be continually put into an organism to replace the energy lost in the form of heat.

Discuss this statement, "Life is an endergonic process." If this is true where do most ibological organisms get their energy?

Ultimately all energy used in by biological organisms comes from light (via
photosynthesis); living organisms must also obtain energy from potential energy
stored in chemical bonds.
Light energy → chemical energy → work